Selecting the right metering pump for your chemical application

Why Metering Pumps are important and how to choose the best option

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A metering pump is designed to move a precise volume of fluid within a specified period of time. This process is referred to as metering or dosing, hence the name metering pump. In most cases, these pumps are used to distribute liquids such as chemicals and solutions. Some common industrial uses for these are water treatment plants, chemical processing plants, and many different agricultural applications just to name a few. It is important to choose a pump that is rated for the temperature, pressure, and fluids used in your applications.

In today world, a metering pump also known as dosing pump is something that is commonly used in many different industries, either used for adding chemicals into a solution or a variety of other things. Due to variations and variety of chemical pumps available, selecting the correct chemical metering pump can be a formidable task. Chemical pumps are designed and constructed out of materials that can withstand substances with varying levels of viscosity, corrosiveness, and abrasiveness. Some chemical pumps are also metering pumps, which provide flow measurement and control for applications that require precise volumes of chemicals.

Chemical pumps can handle applications in many different industries, from general industrial applications to oil and gas, brewery and distillery, semiconductor and others. Corrosion is a major concern with many chemicals. Acids such as sulfuric acid and hydrochloric acid are especially corrosive. In addition to acids, chemicals that pose corrosion problems to varying degrees are chlorine, alkaline solutions, and water. Care must be taken to select a pump manufactured from a material that is compatible with the chemical media.

In addition to chemical media and pump construction materials, what other specifications are the most important to engineers when selecting a chemical pump?

Factors to consider when selecting a chemical pump

The first step in chemical pump selection is a proper understanding of the application requirements and the chemical media properties along with selecting the pump with the specifications to perform the task. However, it is important to pay attention to details and get the experts involved since there are quite a few things to consider when deciding which type of metering pump is best for your application.

The volumes and pressures of material pumped through the equipment may vary greatly for different situations, but it must always be precise. In order for this to work effectively, very specific technology is required.  It is crucial to understand this technology when selecting the proper size and style of your metering pump.

According to Mr. Enrico Gemme, GemmeCotti’s Managing Director, the most important element that needs to be considered while selecting a pump is to understand exactly your needs in order to offer the best solution in terms of materials and design. Sometimes it’s not enough to know the required head, flow, the liquid that has to be pumped and its temperature, but also information about the application are often necessary to find the right solution.

“Moreover, our customers increasingly require a larger customization of the standard product, which can concern materials, pump configuration, pump design or accessories, according to each specific application, and this is another element to be considered during the selection,” said Mr. Enrico Gemme.

A metering pump operates on a fairly simple concept, but there are many factors that influence the style and size of pump that is needed. In order to pick the best metering pump for your application you will need to consider several factors.

Flow Rate

This is one of the most important things to consider. Knowing your expected or desired flow rate is going to be a crucial step in choosing the proper equipment. This is measured in gallons per minute (GPM), although in day-to-day speak, this translates into the pump diameter measurement. A good rule of thumb is to make your maximum expected flow rate no more than 90% of the pump’s capacity. This way you will have room for small increases if needed. Remember: a higher flow rate means a larger pump size is required.

Operating Environment

Here is another one of the first variables you need to keep I mind. Where will the equipment be operating? Is the metering pump going to be outside in direct sunlight? Will it be exposed to below freezing temperatures? This may sound obvious, but it can be overlooked very easily. The operating environment will most definitely impact the performance of the pump. If the pump will be operating in cold temperatures for example, you must make sure the fluid that is being pumped will not freeze at that specific temperature.

Fluid Composition

This is the most important factor when selecting a pump in order to avoid corrosion and unnecessary wear and tear on your pump. The composition of your pumping fluid is also important when deciding on your metering pump type and size. What’s the chemical makeup of the fluid to be pumped? What’s the consistency? Is it a slurry (thick suspension of solids in liquids), or is it a clean fluid? Thicker ones will require the use of special fluid ends. Extremely thick liquids that contain solids may even require special diaphragms in order to operate efficiently.

Pump Construction Materials

Many industries frequently handle corrosive chemicals or abrasive materials that require more heavy duty pump components. It is vital for you to know the chemicals that the pump will be exposed to so that you select a material that is capable of withstanding that chemical exposure. Chemical metering pumps are made from a variety of materials to suit the needs of different applications. For instance, it would be risky to purchase a pump with plastic heads if the chemicals that you use are solvent-based. Such chemicals may dissolve the plastic quickly. Stainless steel may be better option in such a case.

The Desired Capacity

Think about the discharge pressure and flow rate needed in your application before you select a chemical dosing pump. You should avoid over-sizing the pump because it will use a lot of energy during its normal operation.

Nathan Ireland, Export Sales Manager at Amarinth Ltd affirms that, “As with all centrifugal pumps the duty point is the key aspect when selecting the pump sizing. The fluid properties dictate the materials of construction and type of pump needed.”

Select a chemical metering pump that can deliver your desired flow rate or discharge pressure about 85% of its capacity. Such a pump will have the reserve capacity needed to perform when requirements exceed the normal requirements of your application. The pump that you select should also be able to deliver the minimum performance that you desire at about 10-15% of its capacity. Such a pump will be able to be accurate at measuring the small volumes of chemicals that are needed.

Pump Drivers

Select a chemical metering pump whose operating system is compatible with the energy available at your site. For instance, it would be wrong to select a pump that runs on electricity if only natural gas is available at your site.

Leak Protection Mechanisms

You should also consider buying a chemical metering pump that has a system that will alert you in the event of a leak. Such a pump will help you to avoid the accidental discharge of excess amounts of chemicals during the operation of the pump. Some pumps sound alarms in case a leakage is detected within the diaphragm heads of the metering pump. Such a system enables you to respond quickly so that the leak is fixed before it affects your operations.

Viscosity

In order to select the right pump, you need to know the viscosity of the fluid to be pumped. High viscosity fluids require more robust pumping equipment.

Temperature

How hot will the fluid you are pumping be? This will affect which pump materials are best suited for your application.

Pressure

Another factor you should consider when selecting your pump is what the pressure conditions on the inlet and outlet of your pump will be. This information will help you determine the right equipment.

You are likely to select the most appropriate chemical dosing pump for your needs if your selection is based on the factors above. Consult an expert in case you are unsure about how to choose between several pumps that meet the criteria above.